Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

755
FXUS63 KLOT 151123
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
623 AM CDT Mon Jun 15 2026

.KEY MESSAGES...

- Scattered thunderstorms Tuesday with a level 1 for severe
  weather, mainly in the afternoon/early evening.

- Severe thunderstorms Wednesday into Wednesday evening with a
  level 3 for severe weather, with all hazards possible, large
  hail, damaging winds and tornadoes.

- Torrential rainfall and localized flash flooding possible
  Wednesday.

- Possible high waves and dangerous swimming conditions at
  Indiana Lake Michigan beaches Thursday.

&&

.DISCUSSION...
Issued at 225 AM CDT Mon Jun 15 2026

Dry and quiet conditions are expected today with below normal
temps topping out in the mid 70s. Westerly winds will gust into
the 20 mph range.

An upper level trough and associated cold front will move across
the area Tuesday bringing showers and scattered thunderstorms.
There remains some timing differences with activity possibly
into the western cwa Tuesday morning and then strengthening into
the afternoon as it moves across the eastern cwa, likely exiting
the cwa early Tuesday evening. The Day 2 outlook maintains a
level 1 risk for severe weather with moisture/dewpoints being
the limiting factor given current model trends. The NAM does
have a narrow axis of dewpoints in the lower/mid 60s ahead of
the front across northern IN by 00z and if this were to
materialize, there may be a bit higher severe threat in the far
eastern cwa. Prevailing southwest winds ahead of the cold front
may gust into the 30 mph range on Tuesday.

Another stronger upper level trough and associated surface low
will move across the Great Lakes region Wednesday bringing the
threat of severe thunderstorms across much of the region, though
there remains quite a bit of uncertainty for the local area.
There could be ongoing convection midday Wednesday with perhaps
widespread coverage. While there is a chance this could limit
how far north the warm front is able to lift later Wednesday
afternoon into Wednesday evening, the deepening low pressure
that is likely to be north of the area and the strong wind
field may allow the warm front to lift back north through at
least the I-80 corridor and much of the guidance generally
supports the warm front lifting back through at least part of
the local area. Despite these uncertainties, all severe hazards
will be possible Wednesday into Wednesday evening, large hail,
damaging winds and tornadoes, some possibly strong.

Precipitable water values on Wednesday are forecast to be in the
1.5 to 2 inch range across much of the area and the past few
operational runs of the GFS show precipitable water values
across the southern cwa into the 2.25 inch range. Current
forecast qpf amounts for this time period are around 2 inches
for most of the area and if these materialize, combined with the
wet ground and elevated river/creek levels, torrential rain
will lead to localized flash flooding. Too early for a flood
watch but that will need to be considered as Wednesday
approaches.

Prevailing south/southeast winds outside convection Wednesday
may gust into the 30-35 mph range and then shift southwest south
of the warm front. Northwest winds behind the cold front may
also gust into the 30 mph range Wednesday night into Thursday,
but will be dependent on the strengthen/deepening of the system
as it departs. Wind directions may allow for high waves and
dangerous swimming conditions for Indiana Lake Michigan beaches
Thursday.

Quite a bit of uncertainty for the end of the week into next
weekend regarding precip chances. There appears to be a few
weak waves in northwest flow that may allow for some afternoon
showers and thunderstorms Friday and Saturday. And then maybe a
more organized system in the Sunday time frame, which the ECMWF
appears to be fairly consistent with. Temperatures look to
remain slightly below normal through the period. cms

&&

.AVIATION /12Z TAFS THROUGH 18Z TUESDAY/...
Issued at 623 AM CDT Mon Jun 15 2026

Forecast concerns include...

Chance of thunderstorms Tuesday morning.
Gusty southwest winds Tuesday.

Light southwest winds to start will become more west/southwest
by mid morning and increase into the 10-12kt range with gusts
into the 15-20kt by late morning. Winds will diminish under 10kt
with sunset and turn southwest. Speeds and gusts will slowly
begin to increase toward daybreak Tuesday morning and continue
to increase Tuesday morning with gusts into the mid 20kt range.

There will be a chance for showers and thunderstorms Tuesday
morning, mainly after daybreak through mid morning. There
remains uncertainty for both timing and location though there
are some trends in guidance that if thunderstorms occur, this
would be the time period. Despite the low confidence, opted to
include prob thunder mention in the new 30 hour ORD/MDW tafs.
cms

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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